Automatic wind-vaue sight



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July 13,1926. 1,592,487

w. F. GERHARDT AUTOMATIC WIND VANE SIGHT Filed May 17, 1923 2sheets-sheet 1 Cv v s www.

July 13,1926. 1,592,487

W. F. GERHARDT AUTOMATIC WIND VANE SIGHT Filed may 17', 1923 2shuts-sheet 2 (j Aj/7( Eltromw Patented July 13, 1926.

UNITEU STA'iES PATENT GFFICE.

AUTOMATC WNDnVANE SIGHT.

Application led May 1.7, 1923. Serial No. 639,580.

This invention relates to instruments of wind vane sight type to directthe re of a machine gun so as to compensate for the speed of the firingaircraft.

In all flexible aerial machine gun installations a wind vane sight isused to compensate for the speed of the airplane upon which the same ismounted. The principle of the ordinary wind vane sight is well known.These sights heretofore, however, have not been adapted to compensatefor various speeds or to accurately operate in various densities. It is,therefore, the object of the present invention to overcome thedifficulty and unreliability above referred to by providing means forautomatica-lly varying the position of the sight member in proportion tothe speed of the airplane through the air, thus enabling the pro er leadto be obtained on the enemy cra t and provide a much greater accuracy infiring.

A second object of the invention is to provide a compensating device inan automatically adjustable wind vane sight which will correct forchanges in the air density and permit the sight to work accurately atany elevation above the earth.

Further objects will become apparent as the invention is more fully setforth in the attached specification and claims.

In the accompanying drawings- Fig. 1 is a perspective view of theassembled automatically adjustable sight.

Fig. 2 is a transverse section of the sighting member showing the mannerin which it is mounted upon the support.

Fig. 3 is a plan view, partly in section, of the wind pressure vanes andthe housing therefor; and,

Fig. 4 is a vertical section through the housing.

Referring to the drawings by reference numerals, a swivel supportingpost 1 is mounted upon a base 2 to rotate about a. vertical axis, whichis carried upon the, forward part of thermachne' asiiitable mannen Uponthe supporting post 1, are pivotedly mounted two extensible arms 3 and4, mounted by means of pivots 5 and 6, respectively. The arm 3 consistsof a tubular member 7 which slidably supports a rod 8; the arm 4 isconstructed in a similar manner. These slidable rods or arms support avertical rod or standard 9 by means of pivots 10 and 11 and thisstandard carries a sighting bead at its upper end. A flexible Bowdenwire 11 is attached to the sliding rod 8 and extends rearwardly throughthe tubular member 7 and through a flexible casing 12. A similar wire 13extends through a casing'14 and is connected to the rear end of thelower sliding rod in a similar manner. These wires 11 and 13 areoperated in a manner to be hereinafter described.

In order to vary the length of the extensible arms, a supporting housing15 is mounted upon the rear end of the arm 4, and is provided with twovertically extending vanes 16 and 17 which serve to align the wholedevice with the wind about a vertical axis. The upper and lowersurfaces, 18 and 19 of the housing, form horizontal air surfaces whichalign the extensible arms, 3 and 4, with the wind about a horizontalaxis. If desired or found necessary, addi tional horizontal vanes may beprovided on the sides of the housing. In order to supplement the actionof the top and bottom sides of the housin the entire device is balancedabout the pivots, 5 and 6, by means of counterweight 2Origidly'connected t-o the lower extensible arms as shown in Fig. 2.

Vertical vanes 21 and 22 are rigidly mounted upon carriages 23 and 24,respectively, by means of short arms extending through slots in thesides of the housing. These carriages are guided and carried in alongitudinal direction by means of the supporting rods 25 and 26 whichare mounted upon suitable supports in the ends of the housing. A spring27 is provided on each rod between the carriage and an adjustable stop28 provided on the rear end of each rod. These springs tend to force thewind vanes forwardly against the action of the wind which tends to forcethem to the rear. The two carriages 28 and 24 are connected by means `ofa rod 29 which is rigidly attached to each carriage. The motion of thewind vanes as they travel in a longitudinal direction is transmittedfrom this rod 29 by means of a cam slot 80 on a lever 31 pivoted at 32upon the housing. An extension 33 is provided on the lever 31 and aright angular extension 84 is provided on the extension 33 and integralwith the same. The lower end ot the lever extension 34 is pivotallyconnected to a rod 35 which is connected at the point 36 to a wire 37which is connected to the two wires 1l and 13 so as to operate thesewires in unison and equal amounts.

A closed metal bellows 38 is rigidly connected at its upper end toextension 33 ot' the operating lever and at its lower end is pivotallyconnected to a rod 39 which is pivotally connected at its lower end tothe center of the rod 35 and serves to guide the rod 35 as the latter ismoved by the operating lever. This metal bellows serves as acompensating device to correct for changes in air density, as it will beseen that when the device is operated in raretied air the pressureagainst the vanes 21 and 22 will be less for a given speed than whenoperating in a denser air, and, therefore, in order to move the slidingarms the correct distance in this rareed air, the metal bellowscontaining air at atmospheric pressure will expand due to the lessenedexternal pressure on the same so as to suitably position the rod 35 andexaggerate the movements of the wire 37 due to the movements of theOperating lever 3l.

The cam slot 30 is suitably designed so that the backward motion ct thevanes 21 and 22, which is proportional to the square of the velocity ata given density ot the air, will be transformed to a forward motion ofthe wire 37 which will be proportional to the forward velocity at thisdensity. At different densities, the metal bellows will correct themotion of the wire so that it will be compensated to give the correctmotion to the sliding arms. And as the sight supporting standardtogether with the support l constitutes a parallelogram with twohorizontal variable sides the length of which is exactly proportional atall densities to the true airspeed; it is, therefore, seen that anautomatically adjustable wind vane sight is provided which will beycorrect at all speeds thus enabling the proper lead to be obtained inaiming the gun.

I claim:

l. In a wind vane sight, a support, a sight ing member, a slidable arm'carrying said sighting member and mounted on said support, a windpressure operated control unit arranged in the airstream at a distancefrom said sighting member, and means for iin parting movements to saidslidable arm, actuated by said control unit.

2. In a wind vane sight for aircraft, a support, a sighting member, aslidable arm carrying said sighting member and mounted on said support,a wind pressure operated control unit arranged in the airstream at adistance from said sighting member, means for imparting movements tosaid slidable arm actuated by said control unit, and yielding tensioningmeans for said control unit.

3. In a wind vane sight for aircraft, in combination, a support, asighting member, a slidable arm carrying said sighting member pivotedlymounted on said support, a wind vane for controlling the movements ofthe arm and sighting member about the axis of the pivot, a wind pressureoperated control unit arranged in the airstream at a distance from saidsighting member andmeans for imparting movements to said slidable armactuated by said control unit.

4;. In a wind vane sight for tire arms, a support, means for mountingsaid support to rotate about a substantially vertical axis, a sightingmember, a slidable arm carrying said sighting member pivotedl mounted onsaid support, wind vanemeans tor controlling the movements of the armand sighting member about the vertical axis and the axis of said pivotalmount, a wind pressure operated control unit arranged in the airstream,means for imparting movements to said slidable arm actuated by saidcontrol unit so that the distance between the vertical axis and thesighting member will be substantially proportional to the relativevelocity of the air and sight.

5. In a wind vane sight for guns, a support, means for mounting saidsupport on the gun so as to rotate about a substantially vertical axis,a pair of extensible arms pivotedly mounted on said support, a sightingbead carried by said arms, means for keeping the bead and supportaligned with the wind direction, and means for changing the effectivelength of said arms comprising a wind pressure vane, a yielding meansacting on the vane against the torce of the wind, and an auxiliary meansfor compensating for change in air density, whereby the effective lengthof said arms will vary in proportion to the airspeed.

6. In a wind vane sight, a support, means for mounting said support soas t0 rotate about a substantially vertical axis, a pair of extensiblearms pivotally mounted on said support, a sighting bead carried by saidarms, means for keeping the bead and support aligned with the winddirection, and means for changing the effective lengths of said armscomprising a wind pressure vane, a spring connected to the said vane andacting against the torce oi the wind, means for inter-connecting thevane and arms so that the eiiective length of the arms will beproportional to the airspeed and a device inter` posed in said lastmentioned means to correct for the changes in air density.

7. In a wind vane sight, in combination, a support, means for mountingsaid support so as to rotate about a substantially vertical axis, a pairof extensible arms pivotally mounted on said support, a sighting beadcarried by said arms, means for keeping the bead and support alignedwith the Wind direction and means carried by one of said 5 arms forchanging the effect-ive length of said arms comprising a Wind pressurevane held yielding at all times at right angles to the Wind direction, ayielding means acting on the Vane against the force of the Wind and anauxiliary means for compensating 10 for changes in air densitycomprising a link operated by a closed flexible bellows, Whereby theejeetive length of said arms will vary in proportion to the airspeed.

In testimony whereof I afiix my signature.

W. FREDERICK GERIIARDT.

